This project addresses two straightforward questions about physiopathological mechanisms involved in skeletal muscle dysfunction during HF. To this aim we have built locally a network of laboratories and clinical services, used to work together, composed of two services of the University Hospital of Montpellier (Dept. of Cardiology and Dept of Clinical Physiology), an Inserm unit (U637, team 2) all interfaced by an another Inserm facility: the Clinical Investigation Center (CIC) of Montpellier. In this project we will focus on the dilated post-ischemic cardiomyopathy and compare two groups of patients under similar treatments studied at different stages of HF defined by the NYHA. The first patients (class II of NYHA) with a fraction of ejection between 40% and 30 % will be compared with patients (class III) with an ejection fraction lower than 30% (12 males, 35-65 years old per HF). 24 voluntary healthy sedentary individuals carefully selected for similar level of activity as for patients will be matched to the HF groups. All individuals will undergo cardiovascular explorations (ECG and echocardiography, blood test) at the inclusion. They will perform an exercise testing to evaluate their exercise capacity. A muscle biopsy will be performed 4 days after the exercise testing to assess the mitochondrial function and the Ca2+ homeostasis. After a rest period of 5 days, HF patients will perform a resistance-training program (3 times per week for 10 weeks). A 2nd cardiovascular explorations, exercise testing and muscle biopsy will then be performed to evaluate the beneficial effect of training. Mitochondrial function will be measured by oxygraphy and ATP production. Ca2+ homeostasis will be evaluated by confocal microscopy by recording spontaneous Ca2+ release events (i.e. RyR activity). Mitochondrial and RyR biochemical analysis will complete these functional studies as well as circulating factors (cytokines, catecholamine) and their associated receptors.